Red alert: Dead fish and swimming ban due to blue-green algae in Franconia!

Red alert: Dead fish and swimming ban due to blue-green algae in Franconia!

In the last few days, the situation around the waters in Franconia has worsened dramatically. Today, on August 15, 2025, the Süddeutsche points out the acute risks posed by toxic blue-green algae. These are located in several lakes in the region, especially the Altmühlsee, where swimming is strongly discouraged. The lake centers affected are Schlungenhof, Wald and Muhr am See.

In Upper Franconia, the Förmitz dam near Schwarzenbach an der Saale is also affected. A clear bathing warning was issued here. The dangerous blue-green algae can be recognized on the water surface by visible streaks or mats. If the wind brings the algae together in the bank area, this increases the risk for bathers. The city and district of Hof strongly advise against swimming in these areas because the algae are considered particularly toxic.

Health risks and symptoms

The dangers posed by blue-green algae should not be underestimated. A swallowed drink made from contaminated water can lead to serious health problems, including diarrhea and liver and kidney disease. Skin irritations are also often a result of contact with the toxic cyanobacteria. According to the NDR, symptoms of poisoning can include nausea, vomiting, body aches and allergic reactions.

The undifferentiated visibility of the feet in knee-deep water is a rule of thumb: If they can no longer be seen due to a greenish or blue-green cloudiness, it is better to leave your swimming trunks in your pocket. Children and people with previous illnesses who are at risk if they come into contact with the cyanobacteria are particularly at risk.

Causes and developments

Why are blue-green algae blooms increasing so much? This is mainly due to the combination of high temperatures and nutrient inputs into the water. According to Deutschlandfunk, the algae blooms mainly occur at water temperatures above 20 degrees and are particularly popular in dry, warm weather. Overfertilization and climate change have led to an increase in blue-green algae blooms in recent years, which was particularly evident from the hottest summer of 2023 and 2024.

In order to tackle algae in the future, a reduction in nutrient input is essential. Environmental authorities regularly test the water quality in order to issue bathing bans in good time. But while nature is fighting on many fronts, the health of bathers remains the top priority!